PERMFILE123220

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 07h SAR Analysis - EMD
• Media Type: D
• Archive: No

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SAR Analysis for the Eastern Minims District
g'~' Exhibit 7h
V~~.~~~
Introduction
III IIIIIIIIIIIIIIII
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Doc Date:12/11/2001
At [he request of [he Colorado Division of Mines and Geology, Twentymile Coal Company is estimating the
effects of proposed future mine water discharge on water quality in tributary streams to [he Yampa River. These
tributary s[reartts include Foidel Creek, Middle Creek, Fislt Creek, and Trout Creek. Hydro-Geo Consultants.
Inc. (Hydro-Geo) was retained by Twentymile Coal Company to perform this estimate. Mining operations in the
Eastern Mining District currently extract coal from the Wadge Coal Seam. It is proposed [hat these operations
be expanded in coming years to include panels 2 Rigltt - 9 Right on the Wadge Seam. Expansion of ruining
operations will result in additional mine water discharge directly to Foidel Creek, which will potentially impact
water quality further downstream. Estimates of the quantity and quality of mine water discharge are used to
estimate potential impacts in Foidel Creek, Middle Creek, and Trout Creek.
Calculations of Weighted Means and SAR
Water quality parameters (Ca", Mg+', Na`, TDS, and sulfate) were estimated at four points on the tributary
streams to the Yampa River. The first is where the mine discharge Flows will join Foidel Creek, the second is at
Monitoring Station 29 on Middle Creek, the third is at the confluence of Middle Creek and Trout Creek, and the
fourth is at the Fislt Creek-Trout Creek confluence. This is done by combining water quality and Flow data for
each of the streams that contribute to the total Flow at an estimated point. Water quality and flow data were
combined using an equation for calculating a weighted mean:
Ni + N,
where:
m = vveigltted mean for a given water quality parameter (Na, TDS, etc.);
mr = flow in cfs at a given station;
N~ = concentration of a given water quality parameter at a given station.
The calculation of the sodium absorption ration (SAR) for each estimated point is done according to the formula:
SAR = (Na`)
where ion concentrations (irt parentheses) are expressed in milliequivalents per liter.
Sources of Data
• Water quality data for Monitoring Stations 8, 69, 301, and 1003 were taken from Tables33, 46, 44, and 42,
respectiveh~. of the 1993 Annual Hydrology Report (C-82-056) submitted [o [he Colorado Division of Mined
Land Reclarnatiort by Twentymile Coal Company. Flow data (1993 Mean Flow Irrigation Period) for these
stations .vas taken from Table 30 of the same report. These data are mean values for water quality parameters
PR 93-03 EX. 7h-I 3/12/96